The aim of this paper is to introduce a new method for the solution of optimal control problems for which the system is composed by many subsystems whose dynamics are coupled through input-ouput connections. The proposed approach can be regarded as a generalization of the direct multiple shooting method and exploits the structure of the problem to achieve a highly parallelizable algorithm. To demonstrate its effectiveness, the new method is applied to the control of a hydro power plant composed of several connected reaches. (C) 2011 Elsevier Ltd. All rights reserved.